The present invention relates in general to shaft seals, and in particular to a shaft seal using a sealing fluid and having an arrangement for preventing escape of the sealing fluid.
A fluid-sealed shaft seal is known from German OS No. 21 34 964. That prior art shaft seal operates with a single sealing gas, such as helium, nitrogen, or hydrogen. Outlets are provided in a seal ring in circular grooves, to ensure a uniform outflow and, in view of the very small width of the gap, a satisfactory discharge of the fluid. The supply bores are provided within supply grooves which are interrupted and which each extend on the seal ring over a sector of only about 5.degree. to 15.degree.. If a very expensive sealing fluid, such as helium, is employed, it is sought to recover the entire amount thereof. It has been found that in this prior art arrangement, larger amounts of sealing fluid fail to be collected by the discharge grooves and can still escape laterally through the sealing gap itself. It may be provided to produce an underpressure in the discharge grooves, however, this would further require bringing the underpressure into very accurate relationship with the excess pressure of the supplied sealing fluid, and would complicate the operating conditions calling for different specific pressure conditions. U.S. Pat. No. 3,527,465 shows a shaft seal but all of the sealing fluid is first recovered or collected.